1. Field of the Invention
The present invention relates generally to sintered compacts formed mainly of cubic boron nitride (cBN). In particular, the present invention contemplates precisely controlling the sintered compact's catalyst content to provide high-strength, highly thermally conductive sintered compact of cBN excellent in chipping resistance and crater wear resistance.
2. Description of the Background Art
A sintered compact of large hardness formed of cubic boron nitride has conventionally been known. For example, Japanese Patent Laying-Open No.53-77811 discloses a sintered compact of cBN containing 20–80% by volume of cBN, and a Ti ceramic binder as the remainder. The sintered compact, however, does not provide satisfactory life in application to a tool used for interrupted cutting, high speed cutting or similarly, high efficiency cutting. Accordingly the sintered compact is improved in toughness, thermal resistance and the like by improving the binder, covering cBN grains with ceramic to provide enhanced binding strength, improved dispersiveness, and the like.
A sintered compacts with the Ti ceramic binder of Japanese Patent Laying-Open No. 53-77811 improved to provide increased toughness is disclosed for example in Japanese Patent Laying-Open Nos. 56-69350, 61-179847, 61-179848 and 5-287433. The disclosed sintered compact has large toughness and is suitable for interrupted cutting of hardened steel and the like. Furthermore, a binder is placed to surround cBN grains to hold the grains together to provide a sintered compact preventing the grains from being directly bound together, as disclosed in Japanese Patent Laying-Open No. 10-182242. Thus a binder itself is improved or cBN grains prevented from mutual direct contact to attempt to provide a sintered compact of cBN with increased toughness so as to use it for interrupted cutting of hardened steel having large hardness.